The second half of the Tour de France is a key marketplace for riders and teams looking ahead to next season, and none more so than two-time champion Alberto Contador. The Spaniard and his brother/manager Francisco are engaged in a complicated series of negotiations intended to guarantee that the yellow jersey can be retained in 2010. The question everyone wants answered - Contador more than anyone - is which team is most capable of providing him with the back-up required to enable him to deal with what is likely to be a much stiffer challenge next year.

The one team that could ensure Contador will be in the right place to defend his title is also the one team we know he definitely won't be joining. Even before last week's announcement of the impending launch of the RadioShack team, relations were frosty between Contador and old pals Lance Armstrong and Johan Bruyneel. Since the Tour, they've turned glacial.

On Monday, Contador, normally the most uncontroversial of interviewees, declared he had no respect for Armstrong, who countered on his Twitter page that the Spaniard still had a lot to learn. This all makes for a gripping rivalry, but only if the Spaniard can pull together a group of riders able to compete with RadioShack's already impressive-looking roster, which is likely to include Yaroslav Popovych, Haimar Zubeldia, Andreas Klöden, Levi Leipheimer, Gregory Rast and Chris Horner. So what are Contador's options...

Astana: The Kazakh-backed team looked like they were going to struggle to reach the Tour, let alone make it into next season, but their money problems appear to be behind them. From that point of view, they've been boosted by the impending return from a doping ban of Alexander Vinokourov, whose sway within Kazakhstan's government had enabled him to offer Contador a very lucrative extension to his contract, which runs out at the end of next season.

But staying with Astana is problematic in several ways. Firstly, Vinokourov's presence might result in them not being invited to the Tour given it was there he tested positive. Secondly, if invited, Vinokourov may want to push his own overall prospects at the Tour. Thirdly, RadioShack have taken most of its best Tour level riders, leaving behind Contador's small band of Spaniards and a lot of inexperienced Kazakhs. Francisco Contador admits: "Astana, without Armstrong and Bruyneel, is not our preferred option, but Alberto still has a year left on his contract with them."

Garmin-Slipstream: When Astana was near to collapse in May, the American team was close to signing Contador, reportedly backed by a sponsorship deal with supplements supplier Herbalife. Negotiations were also said to include Sergio Paulinho and Benjamin Noval. According to Spanish sports daily AS, Garmin-Slipstream, who showed at the Tour that they weren't keen on playing second fiddle to another American-backed team, is still vying to complete a deal for Contador in order to establish themselves as the direct competition to RadioShack next year. Less convincingly, however, AS also claims that this move will be guaranteed by Bradley Wiggins' transfer to Team Sky in 2010, despite the Briton's insistence just yesterday [Tuesday] that he will see out his contract at Garmin-Slipstream that runs to the end of next season.

Nevertheless, it is noticeable that Garmin-Slipstream is the team most heavily linked with Contador in the Spanish press. Moreover, team manager Jonathan Vaughters has expressed his admiration for the Spaniard, declaring: "Alberto Contador is an incredible rider and would be a fantastic rider to have on any team." Vaughters has also indicated that any signings would be made with the overall benefit of the team in mind. Could this mean Christian Vande Velde and Wiggins joining Paulinho and Noval as a set super-domestiques who would rival those backing Armstrong at RadioShack?

Caisse d'Epargne: The French-backed Spanish team looks the most obvious destination for Contador. He knows the riders and management well, the line-up features plenty of strong domestiques and team leader Alejandro Valverde has admitted he would welcome Contador onto the team and even ride in support of him. The hitch here is that Caisse d'Epargne's commitment only extends to the end of 2010 and Contador is adamant he wants at least a two-year deal. Unless team manager Eusebio Unzue already has new finance lined up, this option looks a non-starter.

Fernando Alonso: The two-time F1 champion announced during the Tour he was launching a team with the aim of one day winning the race and has been heavily linked with Contador. In some ways, this would be the ideal move for Contador; he'd been on a Spanish team as the unquestioned leader. In Alonso's favour is the reported backing of the Banco de Santander, one of the few financial institutions to emerge from the credit crunch with its position strengthened. Note also that the bank's vice-president, Alfredo Saez, was the president of Banesto when they backed Miguel Indurain during his glory years.

However, the dilemma here would be recruiting riders at a level high enough to guarantee Contador would be in contention at the Tour. Speaking earlier this week, Contador's Astana teammate Benjamin Noval admitted: "Alberto loves the idea but he's not interested in it at the moment because the project is too new to put together a team strong enough to win the Tour. He would prefer to go to a team that's already established, that knows what it's doing and can guarantee that he will be well supported." Alonso, it seems, has come to the negotiating table too late and is reported to be delaying the launch of his team.

Katusha: The Russian team not only has the budget to sign Contador and the riders close to him, but can also back that up with plenty of strong and experienced talent of its own, notably Vladimir Karpets, Mikhail Ignatiev, Serguei Ivanov and Alexandre Botcharov. Ivanov's stage win apart, Katusha did not have a great Tour. Well blessed with sprinters and time trial talent, they also lack a stand-out leader for the major tours. It is rumoured that they are planning a big money bid for Contador to fill that gap. Their interest is significant given they have the money, riders and space on the roster to accommodate Contador and his cohort of support riders that also includes Daniel Navarro and Jesus Hernandez.

Other teams: Contador's 1.5-2m euro salary demands puts him well out of reach of the French and Italian teams, but are not beyond the range of Rabobank and Quick Step. However, Contador insists he wants a team "100 percent behind me" and that won't sit well with the likes of Denis Menchov and Oscar Freire at Rabobank, and Tom Boonen at Quick Step. And Team Sky? Signing Contador and co. would very quickly make them major players in the sport, but they already appear to have their roster for 2010 close to completed.